"It is important not to overfeed at this stage because fat laid down in the udder can effect subsequent performance," he says. However, that doesnt mean removing the supplement feed altogether. "Dont under-feed heifers up to 12 months that are destined for 22-24 month calvings," he says. To achieve the correct balance he suggests maintaining a target liveweight gain of up to 0.9kg a day from six months. But at between 6 and 10 months the protein in the ration should be increased and the starch kept out. This can be achieved by offering ad-lib barley straw and 3kg a head a day of maize gluten (20% CP) to give 15% crude protein in the total ration.

Risk of reduced fertility

Underfeeding dairy heifers also runs the risk of reducing fertility.

"It takes 90 days for the egg to develop and the ovary to ovulate it," he says. "Cutting back on feed will upset its growth, producing a smaller follicle and egg – which will impair fertility."

Mr Diepenbroek stresses the need for good quality straw and plenty of it so heifers can be selective if it is to be fed untreated. He says that at £15-£25/t for most producers it will not be cost-effective to feed dairy heifers treated straw.

Ammonia-treated straw – made in a clamp or stack – could be fed ad-lib to animals over six months old alongside 2kg of maize gluten (equivalent to feeding ad-lib untreated and 3kg of maize gluten). But he felt for most producers, feeding an extra 1kg of maize gluten would be easier and more economical.

Caustic-treated straw at £28-£30/t should only be considered for feeding to dairy cows to enhance yield and milk quality, especially in maize-based diets.

Mr Diepenbroek only believes in molasses to enhance feed which is poorly palatable. He urges the need to make feed comparisons on a dry matter basis (see table). "While licks and liquid feeds are convenient, this convenience is costly," he says. For example, those considering a molasses and urea-based blend such as Regumaize 44 are paying £115/t at 64% dry matter or £162/t DM for 33% protein in the fresh weight and would be better off supplementing with rapeseed at £110/t.

He says the table below which gives comparative values (based on ME and CP dry matter values) for alternative feeds could help save money on purchased feeds.

Comparative feed values based on maize gluten and straw

CPMETypicalRelative

MaterialDM%in dry mattercost (£/t)value (£/t)

fresh weight

Maize gluten88.020.412.7110.00110.00

Barley straw86.04.26.570.0070.00

Grass silage (high D)30.016.011.040.0030.20

Grass silage (low D)23.012.010.030.0025.10

Big bale silage50.014.011.075.0059.00

Good quality hay86.09.09.5120.0089.00

Medium quality hay86.08.08.0100.0079.20

Wet brewers grains25.022.011.735.0026.30

Caustic treated wheat78.04.08.592.0086.30

Sodamix*75.09.512.5120.00118.90

Apple pomace25.06.08.525.0025.90

Pressed sugar beet pulp25.013.012.535.0035.00

Imported 16% grass nuts90.017.810.5100.0092.00

Rolled wheat86.012.013.3120.00131.10

Maize silage33.07.011.235.0041.40

&#8226 Comparison of feed values based on ME and CP dry matter values.